1. Field of the Invention
The invention relates to a process for preparing 1-octene by telomerization of 1,3-butadiene using a reducing agent in the presence of a telomerization catalyst and partial hydrogenation of the octadiene obtained in this way.
2. Description of the Background
1-Octene is used in large quantities in the production of various chemical products. For example, surface-active substances, plasticizers, lubricants and polymers are produced from 1-octene. Another large application area is its use as comonomer in polymers, in particular in polyethylene. Virtually all processes utilized commercially at present for producing 1-octene are based on ethene as raw material. Ethene is oligomerized to give a spectrum of α-olefins as main products. If the catalyst and process conditions are chosen appropriately, the amount of 1-octene in the product can be optimized and is then about 25%. Apart from this process, by means of which most of the 1-octene produced is obtained, isolation of 1-octene from the spectrum of products from the Fischer-Tropsch reaction has achieved some importance.
Apart from the processes based on ethene, processes using 1,3-butadiene as raw material for preparing 1-octene are also known from the literature. However, 1-octene cannot be obtained directly, for example via dimerization, from butadiene, but is obtained after a plurality of process steps. 1,3-Butadiene is usually reacted catalytically with a telogen to form a telomer which is fully or partially hydrogenated and subsequently subjected to a cleavage reaction to give the desired 1-octene.
Thus, the patent application WO 92/10450 describes a process in which 1,3-butadiene is reacted with, preferably, methanol or ethanol to form a 2,7-octadienyl ether which, after hydrogenation to the octyl ether, is cleaved to give 1-octene. An analogous route is employed in EP-A-0 440 995, but the reaction in the first step is with a carboxylic acid. The first process step, which is generally referred to as a telomerization, is common to the processes. In the telomerization, a telogen (in EP-A-0 440 995, the carboxylic acid) is generally reacted with a taxogen (1,3-butadiene, 2 equivalents) to form a telomer.
Processes for the catalytic preparation of 1,7-octadienes from 1,3-butadiene have likewise been described in the literature. Thus, EP 12475 and EP 12472 disclose a process for preparing 1,7-octadiene in which butadiene is reacted reductively with formic acid or formates in the presence of organophosphonites and palladium, optionally together with further ligands, to form 1,7-octadiene. Similar processes are described by Raffia et al. in J. Organometal. Chem. 55 (1973), 405–407, who use triphenylphosphine and Pittmann et al. (J. Mol. Chem. 15 (1982) 377–381) who use triethylphosphine and triethylamine as ligands for palladium. The preparation of a 1-olefin is not disclosed in these references.